Agent-based management system having an open layered architecture for synchronous and/or asynchronous messaging handlingUS 6226666 B1

Abstract

A communication infrastructure providing communication between agents, between agents and agent-hosting servers, and between agent-hosting servers. The communication infrastructure consists of three layers (from bottom to top): Mail Facility Layer, Message Facility Layer, and Agent Management Communication Facility Layer. The Mail Facility Layer is the lowest layer providing a general, semantics-free mail paradigm for asynchronous communication between distributed objects, whether they are local or remote to each other. The Mail Facility Layer provides a level of abstraction in terms of mail, virtual mailbox, post office, and mail queue, and hides the details of implementation and actual transport. It is designed to provide location transparency and to be implementable using various transport protocols. The next Message Facility Layer provides a typed messaging paradigm for asynchronous and synchronous message passing between distributed objects. The Message Facility Layer uses the Mail Facility Layer for sending messages and for getting responses to requests sent. It allows for the association of typed message handlers with typed messages such that the format and semantics of messages are encapsulated through their types, are extensible, and can be processed by the associated message handlers. The Agent Management Communication Facility Layer is the highest layer providing the services for inter-agent communication between agents, agent-agent-server communication between an agent and an agent server, and inter-agent-server communication between agent servers for managing agents such as locating an agent, dispatching an agent, retrieving an agent, etc. The key abstractions provided in this layer include agent manager, agent, and agent identifier. It uses the Message

Images(17)

Claims(12)

We claim:

1. A method of providing a communication infrastructure, for communication between independently executing autonomous agents, each of the agents being managed by an agent-hosting server, between the agents and agent-hosting servers, wherein each of the agent-hosting servers can manage one or more of the agents, and between the agent-hosting servers for a distributed computer system, said method comprising the steps of:

communicating mail asynchronously between distributed objects by use of a mail facility layer, the mail facility layer providing a mail object comprising a mail type, a mail identifier, and a mail correlation identifier, the mail identifier uniquely identifying the mail, and the mail correlation identifier associating the mail with another mail;

communicating a message between the distributed objects by use of a message facility layer providing asynchronous and synchronous communication of messages; and

communicating between agents, between agents and agent-hosting servers, and between agent-hosting servers by use of an agent management facility communication layer which manages the agents by locating, dispatching, and retrieving the agents

the message facility layer uses and depends upon the lower mail facility layer;

the lower message facility layer and the lower mail facility layer may be used independently of the upper agent management communication facility layer; and

the lower mail facility layer may be used independently of the upper message facility layer.

2. The method of claim 1 wherein

the mail correlation identifier associates a request message and a response message to the request message by a message handler setting the correlation identifier of the response message to be the message identifier of the request message.

3. The method of claim 1 further comprising the steps of:

encapsulating a message format and message semantics through a message type of the message the message type indicating an allowed message passing mode of the message;

associating a message handler with the message type; and processing the message by the associated message handler.

5. An article of manufacture for use in a distributed computer system for providing a communication infrastructure for communication between independently executing autonomous agents, each of the agents being managed by an agent-hosting server, between the agents and agent-hosting servers, wherein each of the agent-hosting servers can manage one or more of the agents, and between the agent-hosting servers, said article of manufacture comprising a computer-readable storage medium having a computer program embodied in said medium which may cause the distributed computer system to:

communicate mail asynchronously between distributed objects by use of a mail facility layer, the mail facility layer providing a mail object comprising a mail type, a mail identifier, and a mail correlation identifier, the mail identifier uniquely identifying the mail, and the mail correlation identifier associating the mail with another mail;

communicate a message between the distributed objects by use of a message facility layer providing asynchronous and synchronous communication of messages; and

communicate between agents, between agents and agent-hosting servers, and between agent-hosting servers by use of an agent management communication facility layer which manages the agents by locating, dispatching, and retrieving the agents

the message facility layer uses and depends upon the lower mail facility layer;

the lower message facility layer and the lower mail facility layer may be used independently of the upper agent management communication facility layer; and

the lower mail facility layer may be used independently of the upper message facility layer.

6. The article of manufacture of claim 5 wherein

the mail correlation identifier associates a request message and a response message to the request message by a message handler setting the correlation identifier of the response message to be the message identifier of the request message.

7. The article of manufacture of claim 5 wherein the computer program may further cause the distributed computer system to:

encapsulate a message format and message semantics through a message type of the message, the message type indicating an allowed message passing mode of the message;

9. A distributed computer system for providing a communication infrastructure for communication between independently executing autonomous agents, each of the agents being managed by an agent-hosting server, between the agents and agent-hosting servers, wherein each of the agent-hosting servers can manage one or more of the agents, and between the agent-hosting servers, said distributed computer system comprising:

a mail facility layer providing asynchronous communication of mail between distributed objects, the mail facility layer providing a mail object comprising a mail type a mail identifier, and a mail correlation identifier the mail identifier uniquely identifying the mail, and the mail correlation identifier associating the mail with another mail;

a message facility layer providing asynchronous and synchronous communication of messages between distributed objects; and

an agent management communication facility layer providing communication between agents, between agents and agent-hosting servers, and between agent-hosting servers which manages the agents by locating, dispatching, and retrieving the agents

the message facility layer uses and depends upon the lower mail facility layer;

the lower message facility layer and the lower mail facility layer may be used independently of the upper agent management communication facility layer; and

the lower mail facility layer may be used independently of the upper message facility layer.

10. The distributed computer system of claim 9 wherein

the mail correlation identifier associates a request message and a response message to the request message by a message handler setting the correlation identifier of the response message to be the message identifier of the request message.

11. The distributed computer system of claim 9 further comprising:

an encapsulation of a message format and message semantics through a message type of the message, the message type indicating an allowed message passing mode of the message;

A portion of the Disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to agent computer programs, including mobile agents, intelligent agents, collaborating agents, internet agents, and task-specific agents, and more particularly to a communication infrastructure for communication between agents, between agents and agent-hosting servers, and between agent-hosting servers.

2. Description of the Related Art

Java virtual machines are rapidly becoming available on all kinds of computing platforms, from portables to desktops to workstations to mainframes. For the first time in computing history, there may soon be available a virtual, homogeneous platform for distributed and parallel computing on a global scale. The basic elements of this computing platform are distributed Java objects. Prior to JDK 1.1 [The Java Development Kit (JDK), URL=http://java.sun.com/products/jdk], one had to use the low-level socket-based class library (java.net package) for communication between distributed Java objects. With JDK 1.1, one can now use Java RMI (Remote Method Invocation) for direct method invocation between Java distributed objects. Java RMI raises the level of communication to that of objects, and it can pass objects by value using Java object Serialization. However, Java RMI is stationary (remote objects), rigid (predefined methods calls), point-to-point, and connection-oriented. Therefore, it is still too low-level and inflexible for direct use in many applications, such as agent-based applications.

The term “agent” has been used to mean different things in different contexts [D. Chess, B. Grosof, C. Harrison, D. Levine, C. Paris, and G. Tsudik, “Itinerant Agents for Mobile Computing”, IBM Research Report, RC 20010, IBM Research Division, March 1995; C. Harrison, D. Chess, and A. Kershenbaum, “Mobile Agents: Are they a good idea?”, IBM Research Report, IBM Research Division, March 1995.]—from intelligent agents to internet agents to mobile agents to task-specific agents to user agents, just to name a few. A key, distinct characteristic of agents, from our perspective, is that agents are autonomous. An agent has its own identity, thread of execution, and lifecycle. It is this characteristic that makes the agent system, and specifically Java agent system, a unique, flexible and powerful paradigm for distributed and parallel computing [D. T. Chang and D. B. Lange, “Mobile Agents: A New Paradigm for Distributed Object Computing on the WWW”, in Proceedings of the OOPSLA96 Workshop: Toward the Integration of WWW and Distributed Object Technology, October, 1996; MA'97 (First International Workshop on Mobile Agents 97), URL=http:www.informatik.uni-stuttgart.deripvr/vs/ws/ma971ma97.html].

Given that Java agents are autonomous and can be executing independently on various Java virtual machines throughout a vast computer network, what makes them useful and powerful in carrying out parallel and distributed computing is that they must be able to communicate with each other in a dynamic and flexible fashion: the mechanism must allow agents to communicate when one of the agents moves to a different address space (mobile agents), when they must communicate at a higher level than methods calls (intelligent agents), when they need to communicate as a group (collaborating agents), and when a part of computer network is down or one of the agents is not available (disconnected operation).

Voyager defines the notion of a virtual object, which is basically a proxy to a remote object. In Voyager any object can be virtualized using a program called vc, which is a utility for converting regular classes to virtual classes. Messages are sent—via method calls—to remote objects through their local virtual references. Voyager messages can be sent in a synchronous, deferred, or asynchronous (one-way) mode. Object mobility is achieved through sending a “move” message to a remote object.

Concordia supports two types of asynchronous distributed events for inter-agent communication: selected events and group-oriented events. In the select-event messaging, an agent registers the type of events it would like to receive with an event manager. When the event manager receives an event of the registered type it forwards the event to the registered agent. Concordia also supports group-oriented events. An agent can join a group of agents. When one of the agents initiates an event, the event is forwarded to all the agents in the group. Agent mobility is achieved through the use of itineraries, which involves message passing between collaborating Concordia servers.

In Aglets, agents can communicate with each other by sending messages through their proxies. The messages can be sent in a synchronous or deferred mode. Agent mobility is achieved by directly dispatching an agent (through its proxy) or through the use of itineraries. This involves message passing between collaborating agent contexts using the agent transfer protocol.

CORBA [The Common Object Request Broker: Architecture and Specification, Revision 2.0, OMG, July 1995] provides an architecture for stationary objects to communicate with each other in a distributed and heterogeneous environment. It defines a framework for remote method invocation using the IIOP (Internet Inter-ORB Protocol). Under the cover this involves sending request messages and receiving response messages between collaborating hosts.

KQML is a language of communication for intelligent agents. KQML is based on using primitives called performatives. Performatives define permissible actions or operations that agents use for communication. A performative has a name (which specifies what the performative means) and the following fields: sender, receiver, language (language of actual communication: prolog, SQL etc.), ontology (term definitions for the content), correlation id, and content.

Conventional methods have failed to provide a uniform, flexible and robust underlying communication infrastructure for agent systems for communication between agents, between agents and agent-hosting servers, and between agent-hosting servers. Thus, there is a clearly felt need for a method of, system for, and computer program product for, providing a flexible and robust underlying communication infrastructure for agent systems for communication between agents, between agents and agent-hosting servers, and between agent-hosting servers.

SUMMARY OF THE INVENTION

A communication infrastructure providing communication between agents, between agents and agent-hosting servers, and between agent-hosting servers. The infrastructure meets technical requirements for flexibility and robustness: extensible types of messages, asynchronous and synchronous message passing, queuing, disconnected operation, inter-agent communication, and inter-agent-server communication. The communication infrastructure consists of three layers (from bottom to top): Mail Facility Layer, Message Facility Layer, and Agent Management Communication Facility Layer. The communication infrastructure has an open architecture in that a lower layer is designed to be more general than upper layers and can be used independent of the upper layers. Each upper layer, however, is designed to use and depends on the lower layers. The Mail Facility Layer is the lowest layer providing a general, semantics-free mail paradigm for asynchronous communication between distributed objects, whether they are local or remote to each other. The Mail Facility Layer provides a level of abstraction in terms of mail, virtual mailbox, post office, and mail queue, and hides the details of implementation and actual transport. It is designed to provide location transparency and to be implementable using various transport protocols. The next Message Facility Layer provides a typed messaging paradigm for asynchronous and synchronous message passing between distributed objects, whether they are local or remote to each other. The Message Facility Layer uses the Mail Facility Layer for sending messages and, where appropriate, for getting responses to requests sent. It allows for the association of typed message handlers with typed messages such that the format and semantics of messages are encapsulated through their types, are extensible, and can be processed by the associated message handlers. The Agent Management Communication Facility Layer is the highest layer providing the services for inter-agent communication between agents, agent-agent-server communication between an agent and an agent server, and inter-agent-server communication between agent servers for managing agents such as locating an agent, dispatching an agent, retrieving an agent, etc. The key abstractions provided in this layer include agent manager, agent, and agent identifier. It uses the Message Facility Layer and Mail Facility Layer to carry out the communication.

The present invention has the advantage of providing a flexible and robust underlying communication infrastructure for agent systems for communication between agents, between agents and agent-hosting servers, and between agent-hosting servers.

The present invention has the further advantage of providing extensible types of messages.

The present invention has the further advantage of providing asynchronous and synchronous message passing.

The present invention has the further advantage of providing queuing of message passing.

The present invention has the further advantage of providing disconnected operation for inter-agent communication and inter-agent-server communication.

The present invention has the further advantage of allowing implementations of various messaging paradigms to support distributed objects and agent mobility.

T She present invention has the further advantage of allowing implementations of various abstractions to be easily be built on top of the Mail Facility Layer, and facilitating multiple protocol implementations through the Mail Facility Layer.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and the advantages thereof, reference is now made to the Description of the Preferred Embodiment in conjunction with the attached Drawings, in which:

FIG. 1 is a block diagram of a distributed computer system used in performing the method of the present invention, forming part of the apparatus of the present invention, and which may use the article of manufacture comprising a computer-readable storage medium having a computer program embodied in said medium which may cause the computer system to practice the present invention;

FIG. 2 is a block diagram of an agent communication infrastructure in accordance with the present invention;

FIG. 3 illustrates sending a mail through a virtual mailbox using the Mail Facility Layer of the present invention;

FIG. 4 illustrates receiving a mail through a virtual mailbox using the Mail Facility Layer of the present invention;

FIG. 5 illustrates a type hierarchy of messages and a type hierarchy of message handlers in accordance with the Message Facility Layer of the present invention;

FIG. 6 illustrates sending and receiving of a message using the Message Facility Layer of the present invention;

FIG. 8 is a flowchart illustrating the operations preferred in carrying out the send mail portion of the present invention;

FIG. 9 is a flowchart illustrating the operations preferred in carrying out the virtual mailbox portion of the present invention when sending mail;

FIG. 10 is a flowchart illustrating the operations preferred in carrying out the local main post office portion of the present invention when sending mail;

FIG. 11 is a flowchart illustrating the operations preferred in carrying out the destination post office portion of the present invention;

FIG. 12 is a flowchart illustrating the operations preferred in carrying out the receive mail portion of the present invention;

FIG. 13 is a flowchart illustrating the operations preferred in carrying out the virtual mail box portion of the present invention when receiving mail;

FIG. 14 is a flowchart illustrating the operations preferred in carrying out the local main post office portion of the present invention when receiving mail;

FIG. 15 is a flowchart illustrating the operations preferred in carrying out the location post office portion of the present invention;

FIG. 16 is a flowchart illustrating the operations preferred in carrying out the send message portion of the present invention;

FIG. 17 is a flowchart illustrating the operations preferred in carrying out the message portion of the present invention;

FIG. 18 is a flowchart illustrating the operations preferred in carrying out the receive message portion of the present invention;

FIG. 19 is a flowchart illustrating the operations preferred in carrying out the Request/Response Messaging portion of the present invention when sending a request message;

FIG. 20 is a flowchart illustrating the operations preferred in carrying out the Request/Response Messaging portion of the present invention when receiving a request message;

FIG. 21 is a flowchart illustrating the operations preferred in carrying out the Request/Response Messaging portion of the present invention when handling a request message;

FIG. 22 is a flowchart illustrating the operations preferred in carrying out the one-way mode of the Request/Response Messaging portion of the present invention;

FIG. 23 is a flowchart illustrating the operations preferred in carrying out the deferred mode of the Request/Response Messaging portion of the present invention;

FIG. 24 is a flowchart illustrating the operations preferred in carrying out the synchronous mode of the Request/Response Messaging portion of the present invention;

FIG. 25 is a flowchart illustrating the operations preferred in carrying out the agent communication portion of the present invention when a user sends an agent a message;

FIG. 26 is a flowchart illustrating the operations preferred in carrying out the agent communication portion of the present invention when a local main agent manager facilitates an agent message;

FIG. 27 is a flowchart illustrating the operations preferred in carrying out the agent communication portion of the present invention when an owning agent manager facilitates an agent message; and

FIG. 28 is a flowchart illustrating the operations preferred in carrying out the agent communication portion of the present invention when a destination agent manager facilitates an agent message.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference now to the figures and in particular with reference to FIG. 1, there is depicted a pictorial representation of a distributed computer system 8 which may be utilized to implement the method of, system for, and article of manufacture of the present invention. As may be seen, distributed computer system 8 may include a plurality of networks 10 and 32, which may be Local Area Networks (LAN), intranet networks, or internet networks, each of which preferably includes a plurality of individual computers 12 and 30, respectively. Of course, those skilled in the art will appreciate that a plurality of Intelligent Work Stations (IWS) coupled to a host processor may be utilized for each such network.

As is common in such data processing systems, each individual computer may be coupled to a storage device 14 and/or a printer/output device 16. One or more such storage devices 14 may be utilized, in accordance with the present invention, to store the various computer programs which may be accessed and executed by a user within the distributed computer system 8, in accordance with the present invention. In a manner well known in the prior art, each such computer program may be stored within a storage device 14.

Still referring to FIG. 1, it may be seen that distributed computer system 8 may also include multiple mainframe computers, such as mainframe computer 18, which may be preferably coupled to Local Area Network 10 by means of communication link 22. Mainframe computer 18 may also be coupled to a storage device 20 which may serve as remote storage for Local Area Network 10 which may be coupled via communications controller 26 and communications link 34 to a gateway server 28. Gateway server 28 is preferably an individual computer or Intelligent Work Station which serves to link Local Area Network 32 to Local Area Network 10.

As discussed above with respect to Local Area Network 32 and Local Area Network 10, a plurality of server computer programs may be stored within storage device 20 and executed by mainframe computer 18. Similarly, a plurality of client computer programs may be stored within storage devices 14 and executed by individual computers 12 such that distributed client/server computer programs are provided. Of course, those skilled in the art will appreciate that the mainframe computer 18 may be located a great geographical distance from Local Area Network 10, and similarly, Local Area Network 10 may be located a substantial distance from Local Area Network 32. That is, Local Area Network 32 may be located in California while Local Area Network 10 may be located within Texas and mainframe computer 18 may be located in New York.

As will be appreciated upon reference to the foregoing, it is often desirable for a user within one portion of distributed data processing system 8 to execute agent computer programs on one or more portions of data processing system S. For example, the user may execute a client computer program on computer 12 which dispatches a mobile agent to execute on mainframe 18. After obtaining services or information from mainframe 18, the mobile agent may transfer to computer 30 to obtain further services or information from computer 30. Finally, the mobile agent may be retrieved from computer 30 back to computer 12.

System Architecture

The communication infrastructure consists of three layers (from bottom to top):

Mail Facility Layer 210;

Message Facility Layer 220; and

Agent Management Communication Facility Layer 230.

The communication infrastructure has an open architecture in that a lower layer is designed to be more general than upper layers and can be used independent of the upper layers. Each upper layer, however, is designed to use and depends on the lower layers. FIG. 2 illustrates how the Agent Management Communication Facility Layer 230 uses and depends upon the lower Message Facility Layer 220 and Mail Facility Layer 210. FIG. 2 also illustrates how the Message Facility Layer 220 uses and depends upon the lower Mail Facility Layer 210. However, FIG. 2 also illustrates how the lower Message Facility Layer 220 and Mail Facility Layer 210 may be used independently of the upper Agent Management Communication Facility Layer 230, and how the lower Mail Facility Layer 210 may be used independently of the upper Message Facility Layer 220.

The Mail Facility Layer 210 is the lowest layer and the foundation of the communication infrastructure. It provides a general, semantics-free mail paradigm for asynchronous communication between distributed objects such as Java objects, whether they are local or remote to each other. The Mail Facility Layer 210 provides a level of abstraction in terms of mail, virtual mailbox, post office, and mail queue, and hides the details of implementation and actual transport. It is designed to provide location transparency and to be implementable using various transport protocols. Table 2 comprises a package index of the preferred embodiment of the present invention; Table 4 comprises class definitions of the mail package of the preferred embodiment of the present invention; Table 5 comprises class definitions of the mail implementation package of the preferred embodiment of the present invention; Table 8 comprises a class hierarchy of the preferred embodiment of the present invention; and Table 9 comprises an index of all fields and methods of the preferred embodiment of the present invention.

The next layer in the communication infrastructure is the Message Facility Layer 220. It provides a typed messaging paradigm for asynchronous and synchronous message passing between Java objects, whether they are local or remote to each other. The Message Facility Layer 220 uses the Mail Facility Layer 210 for sending messages and, where appropriate, for getting responses to requests sent. It allows for the association of typed message handlers with typed messages such that the format and semantics of messages are encapsulated through their types, are extensible, and can be processed by the associated message handlers. Table 6 comprises class definitions of the message package of the preferred embodiment of the present invention, and Table 7 comprises class definitions of the message handler package of the preferred embodiment of the present invention.

The Agent Management Communication Facility Layer 230 is the highest layer of the communication infrastructure. It provides the services for inter-agent communication between agents, agent-agent-server communication between an agent and an agent server, and inter-agent-server communication between agent servers for managing agents such as locating an agent, dispatching an agent, retracting an agent, etc. The key abstractions provided in this layer include agent manager, agent, and agent identifier. It uses the Message Facility Layer 220 and Mail Facility Layer 210 to carry out the communication. Table 3 comprises class definitions of the agent package of the preferred embodiment of the present invention.

Mail Facility

The Mail Facility Layer 210 provides an asynchronous mail delivery service. Java objects, whether they are local or remote to each other, can use the facility to communicate with each other in an asynchronous manner. A key concept and innovation is that of the virtual mailbox. To send a mail 305, one needs to simply open a virtual mailbox 310 with the name 315 that represents the destination for the mail 305 and put the mail in the virtual mailbox 310. The Mail Facility Layer 210 will do the rest and deliver the mail 305 to the physical destination represented by the name 315, be it local or remote. This is shown in FIG. 3, where Mail 305, Mailbox 310, PostOffice 320, PORemote 325, and MailQueue 330 are Java classes or interfaces.

To receive a mail 405, one again needs to simply open a virtual mailbox 410 with the name 415 that represents the location for the mail and get the mail 405 from the virtual mailbox 410. The Mail Facility Layer 210 will do the rest and retrieve the mail 405 from the physical location represented by the name 415, be it local or remote, as illustrated in FIG. 4.

The Mail Facility Layer 210 uses the abstraction of post office (320, 325, 420, and 425) and mail queue (330, 335, 340, 435, and 440) to encapsulate and hide the details of implementation and actual transport. The post office can be implemented using various transport protocols (345 and 445) and can support multiple transport protocols at the same time. The mail queue (330, 335, 340, 435, and 440) provides the store and forward, and persistence capabilities to support asynchronous and disconnected operations.

Each mail (305 and 405) is designed to have an unique identifier, a correlation identifier, which can be used to correlate related mail, e.g., between responses and requests. To allow for content of various types to be sent and received by mail, each mail has a type specification which is extensible and which does not require name registration. An example of this is given in the discussion of the Message Facility Layer 220. A mail can be given a priority to facilitate its processing by the receiver.

As mentioned before, the virtual mailbox (310 and 410) provides location transparency when sending and receiving mail. Each virtual mailbox 310 is associated with a name 315 which represents some destination or location, local or remote. The name 315 ties it with a certain post office 325, which is the logical home of the virtual mailbox 310. When sending a mail 305, one simply puts it in a virtual mailbox 310 with the appropriate name 315. When receiving a mail 405, one gets it from a virtual mailbox 410 with the appropriate name 415. If needed, one can specify the type or correlation identifier of the mail to be received.

The post office (320, 325, 420, and 425) does the actual sending and receiving of mail. Each post office (320, 325, 420, and 425) is associated with a name (355, 350, 455, and 450 respectively) which represents its location and identification, and which may include the specification of the mail transport protocol (345, 445) (M, IIOP, or MQSeries, for example) to be used by the post office. If the protocol is not specified, the default protocol is implied. A mail 305 can be sent through any known local post office 320, which in turn will deliver the mail 305 to the appropriate destination post office 325. A mail 405 can be received through any known local post office 420, which in turn will retrieve the mail from the appropriate location post office 425, which is the physical location of the mail to be received. If needed, one can specify the type or correlation identifier of the mail to be received.

The post office 320 stores mail in mail queues (330 and 340). It maintains various receiving mail queues 340 for the virtual mailboxes that it owns. Additionally it maintains some sending mail queues 330 which allow it to handle disconnected operation and to optimize mail delivery. The quality of service provided by a mail queue depends on its implementation (e.g., in memory, using files, using databases).

From the above discussion it can be seen that the Mail Facility Layer 210 is a general purpose, asynchronous mail delivery service for Java objects. It forms a flexible and robust foundation for the communication infrastructure. It provides virtual mailboxes for one to send and receive mail in a location transparent manner. The mail can contain various types of content with extensible type specifications. And it utilizes mail queues to provide store and forward, and persistence capabilities.

Message Facility

The Message Facility Layer 220 provides a typed message paradigm for asynchronous and synchronous message passing between Java objects, whether they are local or remote to each other. It allows for the association of typed message handlers (501, 502, 503, 504, 505, and 506) with typed messages (511, 512, 513, 514, 515, and 516 respectively) such that the format and semantics of messages are encapsulated through their types and can be processed by the associated message handlers. As such, both messages and their associated message handlers can be easily extended and doing so without the need of a naming authority. The message type hierarchy 510 and the associated message handler type hierarchy 500 are illustrated in FIG. 5, where Message 511 , MessageHandler 501, etc. are Java interfaces or classes, and arrows are used to indicate inheritance.

An important consideration in the design of the Message Facility Layer 220 is that, in general, agents need to communicate with each other using many different types of messages: event messages [“Concordia: An Infrastructure for Collaborating Mobile Agents”, Mitsubishi Electric ITA, in First International Workshop on Mobile Agents 97 (MA'97), April, 1997; “Mobile Agent Computing”, A White Paper, Mitsubishi Electric ITA, Feb. 28, 1997], KQML messages [InfoSleuth Project, URL=http://www.mcc.com/projects/infosleuth; JKQML, IBM, URL=http://objects.yamato.ibm.com/JKQML/index-e.html; Y. Labrou, “Semantics for an Agent Communication Language”, Ph.D. thesis, CSEE department, University of Maryland, Baltimore Md. 21228-5398, September, 1996. URL=http://www.cs.umbc.edu/kqml], method invocation messages [The Common Object Request Broker: Architecture and Specification, Revision 2.0, OMG, July 1995], request/response messages [Aglets Workbench, IBM, URL=http://www.trl.ibm.co.jp/aglets], etc. A similar consideration is that agent-hosting servers also need to communicate with each other using many different types of messages in order to manage agents: agent transfer messages [Aglets Workbench, IBM, URL=http://www.trl.ibm.cojp/aglets], agent query messages, statistics gathering messages, etc. Therefore, a key requirement in the design of the Message Facility Layer 220 is that it must support multiple types of messages and message handlers, and that it must support their extension and identification with ease. These are accomplished through the use of Java interface/class hierarchies and design patterns.

The Message Facility Layer 220 allows for asynchronous and synchronous message passing. Certain types of messages, such as event messages and KQML messages, are asynchronous in nature and are sent one-way. Other messages, such as method invocation messages and agent transfer messages, involve responses and can be sent in one of three different modes: synchronous (waiting for responses) 2400 of FIG. 24, deferred (getting responses at a later time) 2300 of FIG. 23, or one-way (asynchronous, discarding the responses) 2200 of FIG. 22.

A key design decision and innovation is to integrate the allowed message passing mode with the type of messages rather than treat it as orthogonal to the type of messages. This is based on the observation that for messages such as event messages or KQML messages, it does not make sense to send them in a synchronous or deferred mode. This also allows message definers the freedom to choose the appropriate mode(s) for their types of messages. Table 1 shows exemplary message types in accordance with the preferred embodiment of the present invention.

TABLE 1

Mode

Message Type

Asynchronous One-Way

Synchronous

Deferred

Event

X

KQML

X

Request/Response

X

X

X

Agent Transfer

X

X

To send a message 605 of FIG. 6 via the Message Facility Layer 220, a user first creates a message 605 and then calls send() which creates a mail 610 specifying the type of content and the content wherein the type of content is the type of the message and the content is the message 605. The message 605 also creates a virtual mailbox 615 specifying the virtual mailbox name 620 that represents the destination for the mail 625, which is the receiver virtual mailbox of the message 605. Thereafter, the message 605 puts the mail 610 in the virtual mailbox 615 which causes the Mail Facility Layer 210 to deliver the message 605 to the destination 625.

To receive a message via the Message Facility Layer 220, a user creates a virtual mailbox 665 specifying the virtual mailbox name 670 that represents the physical location 675 of the mail. The user then gets the mail 660, whose content is the message 655, from the virtual mailbox 665 which causes the Mail Facility Layer 210 to get the mail 660 from the location post office 675 through the local main post office 680 into the virtual mailbox 665.

In summary, the Message Facility Layer 220 is a general purpose, message passing service for Java objects and uses the Mail Facility Layer 210 for actual message delivery. It serves as a flexible middle layer for the communication infrastructure. It provides an extensible framework for handling typed messages and associated handlers, and it allows for message passing, where appropriate, in asynchronous, synchronous, or deferred mode.

Agent Management Communication Facility

The Agent Management Communication Facility Layer 230 is the highest layer of the communication infrastructure. It is designed to provide a uniform scheme for handling inter-agent communication, whether the agents involved are stationary or mobile, and inter-agent-server communication. It uses the Message Facility Layer 220 and Mail Facility Layer 210 to carry out the communication.

A key abstraction provided is that of an agent manager (705, 710, and 715). An agent manager manages a group of agents, stationary or mobile, and is responsible for working with other agent managers to locate an agent, send a message to an agent, dispatch an agent, retrieve an agent, etc. Each agent is autonomous and has an agent identifier which uniquely identifies it regardless whether it moves or not. The message passing between agents is illustrated in FIG. 7, where AgentManager (705, 710, and 715) and Agent (720 and 725) are Java classes.

Inter-agent Communication

Communication between mobile agents is done through the collaboration of agent managers. A mobile agent's owning agent manager is aware of an agent's whereabouts at all times and can cause appropriate message forwarding to the current location of an agent. A local agent manager manages agents located at the local agent manager's location or system. If there are one or more local agent managers at a location, then a local main agent manager is the default agent manager. If a mobile agent moves to a location other than that of its owning agent manager, then the managing agent manager at that current location of the agent is known as a destination agent manager.

Each agent manager (705, 710, and 715) owns one or more virtual mailboxes (730, 735, 740, and 790) and uses them to exchange messages (745, 750, and 755) via mail (760, 765, 770, and 785). For example, if an agent manager 705 is asked to send a message 745 to an agent 720, it will generate a mail 760 (with the message 745 encapsulated as its content) and put in the owning agent manager's virtual mailbox 730. The owning agent manager 710 then will, at an appropriate time, receive the message 750, thus causing a mail 765 to be retrieved from its virtual mailbox 735. If the agent 720 is owned and managed by owning agent manager 710, then the owning agent manager 710 will locate the agent 720 and request the agent 720 to handle the message 750.

If the agent 725 is owned, but not managed by, agent manager 710, then the message needs to be redirected to the managing destination agent manager 715. In this situation, owning agent manager 710 generates a mail 785 (with the message 750 encapsulated as its content) and puts the mail 785 in the destination agent manager's 715 virtual mailbox 790. The destination agent manager 715 then will, at an appropriate time, receive the message 755, thus causing a mail 770 to be retrieved from its virtual mailbox 740. The destination agent manager 715 will then locate the agent 725 and request the agent 725 to handle the message 755.

From the above discussion it can be seen that the present invention provides a uniform facility for communication between agents, whether they are stationary or mobile, and for communication between agent managers for the purpose of managing agents, e.g., transferring an agent to a new location.

Referring next to FIG. 8 through FIG. 28, flowcharts illustrating operations preferred in carrying out the present invention are shown. In the flowcharts, the graphical conventions of a diamond for a test or decision and a rectangle for a process or function are used. These conventions are well understood by those skilled in the art, and the flowcharts are sufficient to enable one of ordinary skill to write code in any suitable computer programming language.

Mail Facility Layer Preferred Embodiment

Referring first to FIG. 8 through FIG. 15, the operations preferred in carrying out the Mail Facility Layer 210 of the present invention are illustrated. FIG. 8 through FIG. 11 illustrate the operations preferred in sending mail, and FIG. 12 through FIG. 15 illustrate the operations preferred in receiving mail. To send mail, a user creates a mail 305 specifying the type of content and the content by use of API (Application Program Interface) <new Mail(type, content)>(process block 810 of FIG. 8). The user may also set a response destination for the mail 305 so that a reply may be returned to that destination or so that the mail 305 can be returned in case of delivery failure, <Mail. setResponseDestination(respDest)>(process block 820). The user then creates a virtual destination mailbox 310 by specifying a virtual mailbox name 315 that represents a destination for the mail 325, <new Mailbox(mbName)>(process block 830). The virtual mailbox name 315 comprises a post office name 350 and a mailbox id. The post office name 350 comprises a protocol, host, port, and post office id. This supports multiple protocols (e.g., RMI, which is the default), and the protocol determines the type of post office to be used for sending/receiving mail (e.g., an RMI post office is used in process block 920). Thereafter, the user puts the mail 305 in the virtual mailbox 310, <Mail.putMail(mail)>(process block 840).

Referring next to FIG. 9, the operations preferred in carrying out the virtual mailbox (310 and 900) portion of the Mail Facility Layer 210 of the present invention are illustrated. After the mail 305 has been put into the virtual mailbox 310 by process block 840, process block 920 of FIG. 9 causes the virtual mailbox 310 to get the local main post office 320, <PostOfficeRMI.getLocalPostOffice()>, and process block 930 sends the mail 305 through the local main post office 320, <PostOffice.sendMail(mbName, mail)>.

Referring now to FIG. 10, the operations preferred in carrying out the local main post office (320 and 1000) portion of the Mail Facility Layer 210 of the present invention are illustrated. The local main post office 320 extracts the destination post office name 350 from the virtual mailbox name 315 and uses it to find the destination post office 325, whether local or remote (process block 1010). If the destination post office is not available, then the local main post office 320 may put the mail 305 in the sending mail queue 330 and repeat this step later. This supports disconnected operation. Thereafter, the local main post office 320 generates and sets the mail id for the mail, <Mail.setMailId(mailId)>(process block 1020), and sets the destination for the mail specifying the virtual mailbox name 315, <Mail. setDestination(mbName)>(process block 1030). Process block 1040 then causes the local mail post office 320 to deliver the mail 305 to the destination post office 325 specifying the mailbox id, which is extracted from the virtual mailbox name, <PostOfficeRMI.deliverMail(mbId, mail)>.

Referring now to FIG. 11, the operations preferred in carrying out the destination post office (325 and 1100) portion of the Mail Facility Layer 210 of the present invention are illustrated. After the mail 305 is received at the destination post office 325, the destination post office 325 obtains the receiving mail queue 335 for the mail 305 using the mailbox id (process block 1120), and then the destination post office 325 puts the mail 305 in the mail queue 335, <MailQueue.enqueue(mail)>(process block 1130). Different types of mail queues may provide different quality of service. For example, in-memory mail queue <MemMailQueue>provides fast access, whereas database mail queue <SQLMailQueue>provides persistent storage of mail. The use of these is determined by the post office and is transparent to the user.

Referring now to FIG. 12 through FIG. 15, the operations preferred in receiving mail are illustrated. Referring first to FIG. 12, the user operations preferred in receiving mail via a virtual mailbox 410 are illustrated. A user creates a virtual mailbox 410 specifying the virtual mailbox name 415 that represents the physical location of the mail located at post office 425, <new Mailbox(mbName)>(process block 1210). Thereafter, the user gets the mail 405 from the virtual mailbox 410, <Mail.getMail()>(process block 1220). Alternatively, the user may get the mail with a specific type of content or a specific correlation identifier. The correlation identifier or correlation id associates two or more pieces of mail, for example a mail object and a reply to that mail object.

Referring next to FIG. 13, the operations preferred in the virtual mailbox 410 when receiving mail are illustrated. In response to the user getting the mail 405 from the virtual mailbox 410 (process block 1220), the virtual mailbox 410 gets the local main post office 420, <PostOfficeRMI.getLocalPostOffice()>(process block 1310), and thereafter the virtual mailbox 410 receives the mail 405 through the local main post office 420, <PostOffice.receiveMail(mbName)>(process block 1320). Alternatively, the virtual mailbox may receive the mail with a specific type of content or a specific correlation id.

Referring next to FIG. 14, the operations preferred in the local main post office 420 when receiving mail are illustrated. In response to the virtual mailbox 410 getting the local main post office 420 (process block 1320), the local main post office 420 extracts the location post office name 450 from the virtual mailbox name 415 and uses it to find the location post office 425, whether local or remote (process block 1410). The location post office is the physical location of the mail to be received. If the location post office 425 is not available, the local main post office 420 will repeat process block 1410 later, thus supporting disconnected operation. Thereafter, the local mail post office 420 retrieves the mail 405 from the location post office 425 specifying the mailbox id, which is extracted from the virtual mailbox name 415, <PostOfficeRMI.retrieveMail(mbId, mail)>(process block 1420).

Referring next to FIG. 15, the operations preferred in the location post office 425 when receiving mail are illustrated. In response to the local mail post office 420 retrieving the mail 405 from the location post office 425 (process block 1420), the location post office 425 obtains the receiving mail queue 435 for the mail 405 using the mailbox id (process block 1510), and then gets the mail 405 from the mail queue 435, <MailQueue.dequeue()>(process block 1520). Alternatively, the location post office 425 may get the mail with a specific type of content or a specific correlation id. The mail obtained by process block 1520 is returned to process block 1420 which causes the mail to be returned to process block 1320 which causes the mail to be returned to process block 1220.

Message Facility Layer Preferred Embodiment

Referring now to FIG. 16 through FIG. 18, the operations preferred in carrying out the Message Facility Layer 220 of the present invention are illustrated. FIG. 16 illustrates sending a message, FIG. 17 illustrates the sending of a message via the Mail Facility Layer 210, and FIG. 18 illustrates the receiving of a message.

Referring first to FIG. 16 illustrating the operations preferred in sending a message, a user creates a message 605 of a particular type, <e.g., new KQMLMessage()>(process block 1610). The user sets the sender of the message, <Message.setSender()>(process block 1620); sets the receiver of the message, <Message.setReceiver()>(process block 1630), and sets other attributes of the message as needed, <e.g., KQMLMessage.setPerformative(pero)>(process block 1640). The user then sends the message, <Message. send()>(process block 1650).

Referring next to FIG. 17 illustrating the operations preferred in the sending of a message 605 via the Mail Facility Layer 210, the message 605 creates a mail 610 specifying the type of content and the content wherein the type of content is the type of the message and the content is the message 605, <new Mail(type, content)>(process block 1710). The message 605 may also set a response destination for the mail 610 so that a reply may be returned to the destination or so that it can be returned in case of delivery failure, <Mail.setResponseDestination(respDest)>(process block 1720). The response destination is the sender virtual mailbox of the message. The message 605 also creates a virtual mailbox 615 specifying the virtual mailbox name 620 that represents the destination for the mail 625, <new Mailbox(mbName)>(process block 1730), which is the receiver virtual mailbox of the message 605. Thereafter, the message 605 puts the mail 610 in the virtual mailbox 615, <Mail.putMail(mail)>(process block 1740), which invokes the Virtual Mailbox processing 900 of the Mail Facility Layer 210 starting with process block 920 of FIG. 9 wherein the message 605 is the user of the Mail Facility Layer 210.

Referring next to FIG. 18 illustrating the operations preferred in the receiving of a message via the Message Facility Layer 220, a user creates a virtual mailbox 665 specifying the virtual mailbox name 670 that represents the physical location 675 of the mail, <new Mailbox(mbName)>(process block 1810). The user then gets the mail 660 from the virtual mailbox 665, <Mail.getMail()>(process block 1820), which invokes the Virtual Mailbox processing 1300 of the Mail Facility Layer 210 starting with process block 1310 of FIG. 13 wherein the message 655 is the user of the Mail Facility Layer 210. After process block 1320 has received the mail 660 into the virtual mailbox 665 from the local main post office 680, the user gets the content of the mail 660, which is the message 655, <Mail.getContent()>(process block 1830). Alternatively, process block 1820 may allow the user to optionally get the mail with a specific type of content which represents the type of message to be received.

Request/Response Messaging Preferred Embodiment

Referring next to FIG. 19 through FIG. 24, the operations preferred in carrying out the Request/Response Messaging of the present invention are illustrated. FIG. 19 illustrates the operations preferred in sending a request message; FIG. 20 illustrates the operations preferred in receiving a request message; FIG. 21 illustrates the operations preferred in carrying out the Request Message Handler; FIG. 22 illustrates the operations preferred in a one-way mode of Request/Response Messaging; FIG. 23 illustrates the operations preferred in a deferred mode of Request/Response Messaging; and FIG. 24 illustrates the operations preferred in a synchronous mode of Request/Response Messaging.

Referring next to FIG. 19 illustrating the operations preferred in the sending of a request message, a user first creates a request message, <new RequestMessage()>(process block 1910). The user sets the receiver of the message, <Message.setReceiver()>(process block 1920); the sender of the message, <Message. setsender()>(process block 1930); and other attributes of the message as needed, <e.g., RequestMessage.setOperation(oper)>(process block 1940). Thereafter, the user sends the message, <RequestMessage.send()>(process block 1950) which invokes process block 1650 of FIG. 16 and processing continues by the Message Facility Layer 220.

Referring next to FIG. 20 illustrating the operations preferred in the receiving of a request message, the system (e.g., an agent manager) first creates a virtual mailbox specifying the virtual mailbox name that represents the virtual mailbox, <new Mailbox(mbName)>(process block 2010). The system then gets the mail from the virtual mailbox, <Mail.getMail()>(process block 2020), using the virtual mailbox processing 1300 of FIG. 13, and the content of the mail, which is a clone of the request message, <Mail.getContent(>(process block 2030). Thereafter, the system sets the status of the request message to indicate that it is a clone, <RequestMessage.setClone()>(process block 2040). The system then creates a request message handler, <new RequestMessageHandler()>(process block 2050), and the system asks the request message handler to handle the (cloned) request message, <RequestMessageHandler.handleMessage(reqc)>(process block 2060).

Referring next to FIG. 21 illustrating the operations preferred in the carrying out of the Request Message Handler, the handler handles the message and generates a result (process block 2110). Thereafter, the Request Message Handler determines if a one-way attribute is set (<RequestMessage.isOneway()>) (decision block 2120), and if the one-way attribute is set, then process block 2125 discards the result. Returning now to decision block 2120, if the one-way attribute is not set, then the Request Message Handler creates a response message, <new ResponseMessage(result)>(process block 2130). Thereafter, the Request Message Handler sets a correlation identifier or correlation id of the response message to be the message identifier or message id of the request message, <ResponseMessage.setCorrelationId(corrId)>(process block 2140). The Request Message Handler also sets the receiver of the response message to be the sender of the request message, <Message.setReceiver(receiver)>(process block 2150), and sets the sender of the response message to be the receiver of the request message, <Message.setSender(sender)>(process block 2160). Thereafter, the Request Message Handler sends the response message, <Message.send()>(process block 2170), invoking process block 1650 of the sending message portion 1600 of the Message Facility Layer 220.

Referring next to FIG. 22, FIG. 23, and FIG. 24, three modes of sending the request message and getting the result are illustrated: one-way in FIG. 22, deferred in FIG. 23, or synchronous in FIG. 24.

Referring first to FIG. 22 illustrating the operations preferred in a one-way mode of Request/Response Messaging, if the request message mode is set to one-way before sending (<RequestMessage.setOneway()>), then the request message is sent as a one-way request message, and the result is discarded (process block 2210).

Referring next to FIG. 23 illustrating the operations preferred in a deferred mode of Request/Response Messaging, the user first checks if the result has arrived, <RequestMessage.checkResult()>(process block 2310). Thereafter, the user determines if a the result has arrived (decision block 2320), and if the result has arrived, then the user gets the result (process block 2330). Returning now to decision block 2320, if the result has not arrived, then the user can repeat process block 2310 and decision block 2320 at a later time.

Referring next to FIG. 24 illustrating the operations preferred in a synchronous mode of Request/Response Messaging, the user waits for the result until the result arrives, and gets it, <RequestMessage.getResult(−1)>(process block 2410).

Agent Communication Facility Layer Preferred Embodiment

Referring next to FIG. 25 through FIG. 28, the operations preferred in carrying out the Agent Communication Facility Layer 230 of the present invention are illustrated. FIG. 25 illustrates the operations preferred in carrying out the agent communication portion of the present invention when a user sends an agent a message; FIG. 26 illustrates the operations preferred in carrying out the agent communication portion of the present invention when a local agent manager facilitates an agent message; FIG. 27 illustrates the operations preferred in carrying out the agent communication portion of the present invention when an owning agent manager facilitates an agent message; and FIG. 28 illustrates the operations preferred in carrying out the agent communication portion of the present invention when a destination agent manager facilitates an agent message.

Referring next to FIG. 25 illustrating the operations preferred in carrying out the agent communication facility layer portion of the present invention when a user sends an agent a message, a user first gets the local main agent manager 705, <AgentManager.getLocalAgentManager()>(process block 2510), wherein the local main agent manager is the default agent manager for managing agents located at the local main agent manager's location or system. Thereafter, the user creates a message 745 of a particular type (e.g., KQMLMessage) (process block 2520), and sets the attributes of the message as needed, <e.g., KQMLMessage.setPerformative(perf)>(process block 2530). The user then sends the message through the local main agent manager 705, <AgentManager.sendMessage(aid, msg)>(process block 2540).

Referring next to FIG. 26 illustrating the operations preferred in carrying out the agent communication facility layer portion of the present invention when a local agent manager facilitates an agent message, the local main agent manager 705 first sets the receiver of the message to the owning agent manager 710 URL (Uniform Resource Locator) in string form concatenated with the agent id in string form, <Message.setReceiver(receiver)>(process block 2610). The owning agent manager is aware of an agent's whereabouts at all times and can cause appropriate message forwarding to the current location of an agent. The local main agent manager 705 also sets the sender of the message to the its URL (string form), <Message. setSender(sender)>(process block 2620), and then sends the message, <Message.send()>(process block 2630), invoking process block 1650 of the sending message portion 1600 of the Message Facility Layer 220.

Referring next to FIG. 27 illustrating the operations preferred in carrying out the agent communication facility layer portion of the present invention when an owning agent manager facilitates an agent message, the owning agent manager 710 first creates a virtual mailbox 735 specifying the virtual mailbox name 775 that represents it's virtual mailbox wherein the virtual mailbox name is a string form of its URL, <new Mailbox(mbName)>(process block 2710). Thereafter, the owning agent manager 710 gets the mail 765 from the virtual mailbox 735, <Mailbox.getMail(>(process block 2720), and gets the content of the mail 765, which is the message 750, <Mail.getContent()>(process block 2730). The owning agent manager 710 also gets the receiver 720 of the message wherein the receiver is the agent id in string form, <Message.getReceiver)>(process block 2740), and gets the managed and owned agent 720, <AgentManager.getAgent(aid)>(process block 2750). Thereafter, the owning agent manager 710 determines if an agent 720 exists locally (decision block 2760), and if the agent 720 exists locally, then the owning agent manager 710 asks the managed agent 720 (managed agent if local) to handle the message 750, <Agent.handleMessage()>(process block 2770). Returning now to decision block 2760, if the agent does not exist locally (if the agent has moved to a location managed by a different agent manager 715), then the owning agent manager 710 gets the destination 715 of the owned agent 725 wherein the destination is the URL in string form of the destination agent manager 715 (process block 2775). This is the situation where the agent 725 has moved away from it's owning agent manager 710. Whenever it does so, the owning agent manager 710 is informed of it's new destination and the destination agent manager 715. Thereafter, the owning agent manager 710 sets the receiver of the message wherein the receiver is set to the destination agent manager 715 URL in string form concatenated with the agent id in string form, <Message.setReceiver(receiver>(process block 2780). The owning agent manager 710 then sends the message 755, <Message.send()>(process block 2790).

Referring next to FIG. 28 illustrating the operations preferred in carrying out the agent communication portion of the present invention when a destination agent manager facilitates an agent message, the destination agent manager creates a virtual mailbox specifying the virtual mailbox name that represents it's virtual mailbox wherein the virtual mailbox name is a string form of it's URL, <new Mailbox(mbName)>(process block 2810). The destination agent manager is the managing agent manager at the current location of the agent if the agent moves to a location other than that of its owning agent manager. Thereafter, the destination agent manager gets the mail from the virtual mailbox, <Mailbox.getMail()>(process block 2820); gets the content of the mail which is the message, <Mail.getContent()>(process block 2830); and gets the receiver of the message wherein the receiver is the agent id in string form, <Message.getReceiver()>(process block 2840). The destination agent manager then gets the managed and owned agent, <AgentManager.getAgent(aid)>(process block 2850), and asks the managed agent to handle the message, <Agent.handleMessage()>(process block 2860).

Although the present invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the spirit and the scope of the invention.

TABLE 2

API User's Guide Class Hierarchy Index

Package Index

Other Packages

package com.ibm.jma.agent

package com.ibm.jma.mail

package com.ibm.jma.mail.input

package com.ibm.jma.message

package com.ibm.jma.message.handler

TABLE 3

All Packages Class Hierarchy Index

package com.ibm.jma.agent

Class Index

Agent

AgentID

AgentManager

Exception Index

AgentException

All Packages Class Hierarchy This Package Previous Next Index

Class com.ibm.jma.agent.Agent

java.lang.Object

. . . com.ibm.jma.agent.Agent

public abstract class Agent

extends Object

implements Cloneable, MessageHandler

This is the abstract, Toot class of all agents, stationary or mobile. Each agent has a globally unique identifier and is managed by an agent manager. An agent can communicate with other agents using messages.

See Also:

AgentManager, AgentID, Message

Constructor Index

Agent()

Method Index

getID()

Gets the identifier of this agent.

GetManager()

Gets the (current) agent manager of this agent.

getMessageTypes()

Gets the message types which can be handled by this agent.

handleMessage(Message)

Handles the specified message.

init(AgentManager, AgentID, Object)

Constructors

Agent

protected Agent()

Methods

init

protected void init(AgentManager am, AgentID aid, Object init)

getID

public final AgentID getID()

Gets the identifier of this agent

getManager

public final AgentManager getManager()

Gets the (current) agent manager of this agent.

handleMessage

public boolean handleMessage(Message msg)

Handles the specified message.

getMessageTypes

public String getMessagetypes()

Gets the message types which can be handled by this agent

Returns:

message types concatenated in a string and separated by spaces.

All Packages Class Hierarchy This Package Previous Next Index

All Package Class Hierarchy This Package Previous Next Index

Class com.ibm.jma.agent.AgentID

java.lang.object

. . . com.ibm.jma.agent.AgentID

public final class AgentID

extends Object

implements Serializable

An AgentID object encapsulates an agent's identifier.

Constructor Index

AgentID(byte[])

Constructs an agent identifier from the specified byte array representation.

AgentID(String)

Constructs an agent identifier from the specified string representation.

Method Index

equals(Object)

Test if the specified object is an agent identifier and is equal to this agent identifier.

getID()

Gets the byte array representation of this agent identifier.

hashCode()

Returns the hash code for this agent identifier.

toString()

Gets the string representation of this agent identifier.

Constructors

AgentID

public AgentID(byte bid[])

Constructs an agent identifier from the specified byte array representation.

AgentID

public AgentID(String sid)

Constructs an agent identifier from the specified string representation.

Methods

getID

public byte[] get()

Gets the byte array representation of this agent identifier.

toString

public String toString()

Gets the string representation of this agent identifier.

Overrides:

toString in class Object

equals

public boolean equals(Object obj)

Test if the specified object is an agent identifier and is equal to this agent identifier.

Overrides:

equals in class Object

hashCode

public int hashcode()

Returns the hash code for this agent identifier.

Overrides:

hashCode in class Object

All Packages Class Hierarchy This Package Previous Next Index

All Packages Class Hierarchy This Package Previous Next Index

Class com.ibm.jma.agent.AgentManager

java.lang.Object

. . . com.ibm.jma.agent.AgentManager

public final class AgentManager

extends Object

implements MessageHandler

An agent manager manages agents, stationary or mobile, including their communication, mobility, etc. Each agent manager may collaborate with other agent managers to accomplish its tasks.

See Also:

Agent, AgentID, Message

Field Index

DEFAULT_AM_NAME

DEFAULT_PORT_NUMBER

DEFAULT_PROTOCOL

Method Index

createAgent(URL, String, Object)

Creates an agent with the specified codebase, class name, and initialization.

dispatchAgent(agent, String)

Dispatches an agent to the specified destination.

getAgent(AgentID)

Gets the agent managed by this agent manager with the specified agent identifier.

getAgents()

Gets all agents managed by this agent manager.

getDestination(Agent ID)

Gets the destination of the agent owned by this agent manager.

getLocalAgentManager()

Gets the local agent manager.

getMessageTypes()

Gets the message types which can be handled by this agent manager.

getName()

Gets the name of this agent manager.

getURL()

Gets the url of this agent manager.

handleMessage(Message)

Handles the specified message.

retrieveAgent(AgentID)

Retrieves the agent with the specified agent identifier.

sendMessage(AgentID, Message)

Sends the specified message to the agent with the specified identifier.

This method receives mail with correlation id “corrId” with timed wait of “waitTime” milliseconds from mailbox “mbName” when it times out a null mail object is returned

Parameters:

mbName—Name of the mail box from which to receive

corrId—Correlation Id of the mail to be received

waitTime—Number of milliseconds to wait

All Packages Class Hierarchy This Package Previous Next Index

All Packages Class Hierarchy This Package Previous Next Index

Class com.ibm.jma.mail.Mail

java.lang.object

. . . com.ibm.jma.mail.Mail

public class Mail

extends Object

implements Serializable

A Mail object is used to transport typed content. Each mail has a type and a content. The format and semantics of the content depends on the content type.

constructor Index

Mail()

Mail(Mail)

Mail(String, Object)

Constructs a mail with the specified content type and content.

Methods Index

getContent()

Returns the content of this mail.

getCorrelationID()

Returns the correlation id.

getDestination()

Returns the destination of this mail.

getMailID()

Returns the mail id of this mail.

getPriority()

Returns the priority of this mail

getResponseDestination()

Returns the response destination of this mail.

getType()

Returns the content type of this mail.

setCorrelationId(byte[])

Sets the correlation id for the mail that this mail corresponds to.

setDestination(String)

Sets the destination of this mail

setMailId(byte[])

Sets the mail id of this mail.

setPriority(int)

Sets the priority of this mail.

setResponseDestination(String)

Sets the response destination of this mail.

toString()

Returns a string representing this mail.

Constructors

Mail

public Mail(String type, Object content)

Contructs a mail with the specified content type and content.

Parameters:

type—the content type of this mail

content—the content of this mail

Mail

protected Mail()

Mail

protected Mail(Mail m)

Methods

toString

public String toString()

Returns a string representing this mail.

Overrides:

toString in class Object

getType

public String getType()

Returns the content type of this mail.

getContent

public Object getContent()

Returns the content of this mail.

setMailId

public void setMailId(byte id[])

Sets the mail id of this mail.

getMailId

public byte[] getMailId()

Returns the mail id of this mail.

setCorrelationId

public void setCorrelationId(byte id[])

Sets the correlation id for the mail that this mail corresponds to. Required for a response mail.

getcorrelationId

public byte[] getCorrelationId()

Returns the correlation id.

setPriority

public void setPriority(int priority)

Sets the priority of this rail. The priority ranges from 1 to 10. The default is 5.

getPriority

public int getPriority()

Returns the priority of this mail

setDestination

public void setDestination(String dest)

Sets the destination of this mail

getDestination

public String getDestination()

Returns the destination of this mail.

setResponseDestination

public void setResponseDestination(String respDest)

Sets the response destination of this mail.

getResponseDestination

public String getResponseDestination()

Returns the response destination of this mail

All Packages Class Hierarchy This Package Previous Next Index

All Packages Class Hierarchy This Package Previous Next Index

Class com.ibm.jma.mail.Mailbox

java.lang.object

. . . com.ibm.jma.mail.Mailbox

public class Mailbox

extends Object

A Mailbox object is used to send (put) and receive (get) mail. A mailbox is virtual. To send a mail, one simply opens a mailbox with the name that represents the destination for the mail and puts the mail in the mailbox. To receive a mail, one again simply opens a mailbox with the name that represents the location for the mail and gets the mail from the mailbox.

See Also:

Mail

Constructor Index

Mailbox(String)

Constructs (opens) a mailbox with the specified name.

Method Index

getMail()

Gets (receives) a mail from this mailbox.

getMail(byte[])

Gets (receives) a mail with the specified correlation id from this mailbox.

(byteMail[], long)

Gets (receives) a mail with the specified correlation id from this mailbox , waiting if the mail arrives within the specified wait time.

getMail(long)

Gets (receives) a mail from this mailbox, waiting if the mail arrives with the specified wait time.

getMail(String)

Gets (receives) a mail with the specified content type from this mailbox.

getMail(String, long)

Gets (receives) a mail with the specified content type from this mailbox, waiting if the mail arrives within the specified wait time.

getName()

Returns the name of this mailbox.

getMail(Mail)

Puts a mail in this mailbox (i.e., sends a mail to this mailbox).

Constructors

Mailbox

public Mailbox(String name)

Constructs (opens) a mailbox with the specified name.

Methods

getName

public String getName()

Returns the name of this mailbox.

putMail

public byte[] putMail(Mail mail)

Puts a mail in this mailbox (i.e., sends a mail to this mailbox).

Parameters:

mail—the mail to be sent

Returns:

the mail id of the mail sent

getMail

public Mail getMail()

Gets (receives) a mail from this mailbox. If there is no mail, it returns null.

Returns:

a mail

getMail

public Mail getMail(long waitTime)

Gets (receives) a mail from this mailbox, waiting if the mail arrives within the specified wait time. If the wait time is set to −1, it waits forever until the mail arrives.

Returns:

a mail

getMail

public Mail getMail(String type)

Gets (receives) a mail with the specified content type from this mailbox. If there is no such mail, it returns null.

Returns:

a mail with the specified content type

getMail

public Mail getMail(String type, long waitTime)

Gets (receives) a mail with the specified content type from this mailbox, waiting if the mail arrives within the specified wait time. If the wait time is set to −1, it waits forever until the mail arrives.

Parameters:

type—the content type of the mail to be received

waitTime—the time (in msecs) to wait for the mail to arrive

Returns:

a mail with the specified content type

getMail

public Mail getMail(byte corrId[])

Gets (receives) a mail with the specified correlation id from this mailbox. If there is no such mail, it returns null.

Returns:

a mail with the specified correlation id

getMail

public Mail getMail(byte corrId[], long waitTime)

Gets (receives) a mail with the specified correlation id from this mailbox waiting if the mail arrives within the specified wait time. If the wait time is set to −1, it waits forever until the mail arrives.

A ATResponseMessage object is used to send back the result of an agent request message.

See Also:

RequestMessage

Constructor Index

ATResponseMessage(Object)

Constructs an agent transfer response message with the specified result.

Method Index

getParameters()

Gets the parameters of the result.

setParameters(Hashtable)

Sets the parameters of the result

Constructors

ATResponseMessage

public ATResponseMessage(Object result)

Constructs an agent transfer response message with the specified result.

Methods

setParameters

public void setparameters(Hashtable params)

Sets the parameters of the result

getParameters

public Hashtable getparameters()

Gets the parameters of the result.

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All Packages Class Hierarchy This Package Previous Next Index

Class

com.ibm.jma.message.KQMLMessage

Java.lang.object

. . . com.ibm.jma.message.Message

. . . com.ibm.jma.message.KQMLMessage

public class KQMLMessage

extends Message

A KQMLMessage object is used to send messages following the KQML format and protocol.

Constructor Index

KQMLMessage()

Constructs a KQML message.

Method Index

getContent()

Gets the content

getInReplyTo()

Gets the identifier that this message is replying to.

GetInReplyWith()

Gets the identifier that this message is to be relied with.

getLanguage()

Gets the content language.

getOntology()

Gets the content ontology.

getPerformative()

Gets the performative.

setContent(Object)

Sets the content.

setInReplyTo(String)

Sets the identifier that this message is replying to.

setLanguage(String)

Sets the content language.

setOntology(String)

Sets the content ontology.

setPerformative(String)

Sets the performative.

setReplyWith(String)

Sets the identifier that this message is to be relied with.

Constructors

KQMLMessage

public KQMLMessage()

Constructs a KQML message.

Methods

setperformative

public void setPerformative(String perf)

Sets the performative.

getPerformative

public String getperformative()

Gets the performative.

setInReplyTo

public void setInReplyTo(String int)

Sets the identifier that this message is replying to.

getInReplyTo

public String getInReplyTo()

Gets the identifier that this message is replying to.

setReplyWith

public void setReplyWith(String rw)

Sets the identifier that this message is to be relied with.

getInReplyWith

public String getInReplyWith()

Gets the identifier that this message is to be relied with.

setLanguage

public void setLanguage(String lang)

Sets the content language.

getLanguage

public String getLanguage()

Gets the content language.

setOntology

public void setOntology(String onto)

Sets the content ontology.

getOntology

public String getOntology()

Gets the content ontology.

setContent

public void setContent(Object content)

Sets the content.

getContent

public Object getContent()

Gets the content.

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Class com.ibm.jma.message.Message

java.lang.object

. . . com.ibm.jma.message.Message

public abstract class Message

extends Object

implements Serializable

This is the abstract, root class of all types of messages. A Message object is used to encapsulate the information which is to be sent from a sender to a receiver. Its class name represents its type, which determines its format and semantics. Each type of messages may be associated with a corresponding type of message handlers which are designed to handle the messages.

See Also:

MessageHandler

Field Index

mailID

Constructor Index

Message()

Method Index

getReceiver()

Gets the receiver mailbox of this message.

getReceiverMB()

Gets the sender of this message.

getSender()

Gets the sender mailbox of this message.

getSenderMB()

Gets the sender mailbox of this message

send()

Sends this message to the receiver.

setReceiver(String)

Sets the receiver of this message.

setSender(String)

Sets the sender of this message.

Fields

mailId

protected byte mailId[]

Constructors

Message

public Message()

setsender

public void setSender(String sender)

Sets the sender of this message.

getSender

public String getSender()

Gets the sender of this message.

getSenderMB

public String getSenderMB()

Gets the sender mailbox of this message.

setReceiver

public void setReceiver(String receiver)

Sets the receiver of this message.

getReceiver

public String getReceiver()

Gets the receiver of this message.

getReceiverMB

public String getReceiverMB()

Gets the receiver mailbox of this message.

send

public void send()

Sends this message to the receiver. This operation uses the Jamaica Mail Facility (com.ibm.jma.mail) to accomplish its task.

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All Packages Class Hierarchy This Package Previous Next Index

Class

com.ibm.jma.message.RequestMessage

java.lang.Object

com.ibm.jma.message.Message

. . . com.ibm.jma.message.RequestMessage

public class RequestMessage

extends Message

A RequestMessage object is used to send messages which return a result. A request message can be sent in three different modes: one-way (asynchronous, discarding the result), synchronous (blocking until the result arrives), or deferred (obtaining the result at a later time). The result of a request message is contained in a response message.

See Also:

Constructs a request message.

Constructor Index

RequestMessage()

Constructs a request message

Method Index

checkResult()

Tests if the result has arrived.

getMessageID()

Gets the message id.

getOperation()

Gets the operation to be performed by the receiver of this message.

getParameters()

Gets the parameters of the operation.

getResult()

Gets the result.

getResult()

Gets the result if it arrives within the specified wait time.

isClone()

Tests if this message is a clone.

isOneway()

Tests if the messaging mode is one-way.

isRead()

Tests if the result has been read.

isSend()

Tests if this message has been sent

send()

Sends this message.

setClone()

Indicates that this message is a clone.

setMessageID(byte[])

Sets the message id.

setOneway()

Sets the messaging mode to one-way.

setOperation(String)

Sets the operation to be performed by the receiver of this message.

setParameters(Hashtable)

Sets the parameters of the operation.

Constructors

RequestMessage

public RequestMessage()

Constructs a request message.

Methods

setMessageId

protected void setMessageID(byte msgId[])

Sets the message id.

getMessageId

public byte[] getMessageId()

Gets the message id.

setOneway

public void setoneway()

Sets the messaging mode to one-way. The result, if any, will be discarded.

isOneway

public boolean isoneway()

Tests if the messaging mode is one-way.

setOperation

public void setoperation(String oper)

Sets the operation to be performed by the receiver of this message.

getOperation

public String getoperation()

Gets the operation to be performed by the receiver of this message.

setparameters

public void setParameters(Hashtable params)

Sets the parameters of the operation.

getParameters

public Hashtable getparameters()

Gets the parameters of the operation.

send

public void send()

Sends this message.

Overrides:

send in class Message

isSent

public boolean isSent()

Tests if this message has been sent

setClone

public void setclone()

Indicates that this message is a clone.

isClone

public boolean isclone()

Tests if this message is a clone.

checkResult

public boolean checkResult()

Tests if the result has arrived.

getResult

public Object getResult()

Gets the result. If the result has not arrived, returns null.

getResult

public Object getResult(long waitTime)

Gets the result if it arrives within the specified wait time. If the wait time is set to −1, waits forever until the result arrives.

Returns:

the result

isRead

public boolean isread()

Tests if the result has been read.

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All Packages Class Hierarchy This Package Previous Next Index

Class

com.ibm.jma.message.ResponseMessage

java.lang.Object

com.ibm.jma.message.Message

com.ibm.jma.message.ResponseMessage

public class ResponseMessage

extends Message

A ResponseMessage object is used to send back the result of a request message.

See Also:

RequestMessage

Constructor Index

ResponseMessage(Object)

Constructs a response message with the specified result.

Method Index

getCorrelationId()

Gets the correlation id.

getResult()

Gets the result that this message contains.

setCorrelationId(byte[])

Sets the correlation id for the corresponding request message.

Constructors

ResponseMessage

public ResponseMessage(Object result)

Constructs a response message with the specified result.

Methods

setCorrelationId

public void setCorrelationId(byte corrId[])

Sets the correlation id for the corresponding request message.

getCorrelationId

public byte[] getCorrelationId()

Gets the correlation id.

getResult

public Object getResult()

Gets the result that this message contains.

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TABLE 7

All Packages Class Hierarchy Index

package com.ibm.jma.message.handler

Interface Index

MessageHandler

Class Index

ATRequestMessageHandler

ATResponseMessageHandler

KQMLMessageHandler

KSQLMessageHandler

RequestMessageHandler

ResponseMessagHandler

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Interface

com.ibm.jma.message.handler.MessageHandler

public interface MessageHandler

This interface is implemented by all message handlers. Each type of message handlers is designed to handle an associated type(s) of messages.

Electronic messaging method of and system for heterogeneous connectivity and universal and generic interfacing for distributed applications and processes residing in wide variety of computing platforms and communication transport facilities